The sacU operon of Bacillus subtilis has previously been shown to regulate the expression of extracellular enzymes involved in the degradation of complex polysaccharides and proteins. Southern blot analysis of Streptococcus mutans chromosomal DNA using the sacU operon as a gene probe indicates that this organism also contains similar genes. Given that degradative genes similar to those mentioned above have been demonstrated to be involved in cariogenesis, it is then likely that. these sacU-like genes play a major role in determining the virulence of S. mutans. To study this hypothesis, the sacU-like genes of S. mutans GS-5 will be cloned and sequenced. The cloned DNA will then be utilized to construct a sacU null mutation by insertional mutagenesis and those genes affected by this mutation will be determined by assaying for the alteration of the synthesis of various exoenzymes.